Because alot of armors do the same thing. Not only that but each armor should have back ups.

Tony currently is just improving his armors, thus the mach 1-42. He's not been starting from scratch and building a new armor.... The rumored hulk buster and space armor would be the first ones to break that trend. These arnt upgrades they're situation specific.

Tonys basic armors also do many things that some individual armor do in the comics... Does he really need a "volcano suit" , "subterranean armor" , "underwater" armor?, stealth? No... His basic suit should be able to do all that with upgrades.... Its not like the hellicarrier needed painted dark blue to be stealthy....

That's a good point, I didn't think about it like that. I just wanted to see a crap load of different armors like in the comics.